1. Field of the Invention
The present invention relates to a method and an apparatus for controlling document printing, onto a printing paper, in a line printer.
2. Description of the Related Art
In recent years, line printers have been put into practical use. The printers use continuous paper and, particularly, folded printing paper with perforations and print, at a high speed, data sent from a host computer which is the data processor.
In such a line printer, in general, the data to be printed are transmitted from the host computer to a character data processing portion of the line printer. The data to be printed are sequentially converted into codes for the line printer by the character data processing portion in the control unit of the line printer, and are stored in a buffer. Code data, for one page, that are stored in the buffer are then read out line by line by a character conversion portion of the line printer, converted into character patterns corresponding to the codes, and are stored in a bit map memory as an image data. The conversion into character patterns corresponding to the codes is carried out based upon a character font stored in a ROM in the line printer.
After the code data of one page are converted into character patterns and are stored in a bit map memory, the contents (=the image data) of the bit map memory are sent to a print control mechanism in the line printer and are printed onto the continuous paper.
In the above line printer, in which the speed for feeding the printing paper has been predetermined, there remains a problem in that the same amount of time is required for printing a document irrespective of the width of the document. That is, when the line printer prints a document onto the printing paper, the document having a width which is smaller than one-half the printable width of the printing paper, the same amount of printing time is required irrespective of the width of the document when the paper is fed at a predetermined speed, since the data of one document are not expanded in the bit map memory.
To correct this situation, the following method can be contrived.
(1) Character data of the same lines of two documents are combined together as printing data of one line by the host computer, and are sent to the line printer.
(2) Character data of the same lines of two documents are converted into codes as the printing data of one line, and are stored in the buffer.
(3) Code data of the same lines of two documents are converted into character patterns and are stored in the bit map memory in a state where the data of the two documents are stored in the buffer that corresponds to a page of the printing paper.
(4) After character pattern data of two documents are all stored in the bit map memory, the print control mechanism of the line printer is driven to print the two documents on a single piece of paper.
In order to realize this method, in which a plurality of documents are processed as one document, the software must be changed on the host computer side requiring considerable time and effort to change the software. When the software of the host computer is changed, furthermore, trouble may occur on the host computer side due to the change in the software.